These studies deal with development of optimal screening strategies for cervical neoplastic disease and adenocacinoma of the endometrium and their precursor lesions. Using a theoretical model of the natural history of these diseases and available data from sources such as the Third National Cancer Survey, methods of evaluating the effects of different screening strategies on incidence, survival, and mortality in the population at large or selected subsets at differential risk are being developed. Screening for cervix lesions on an annual basis was instituted empirically. Changes in intervals between successive examinations have been suggested based on estimates of differential risk of incidence. The results of such changes in screening together with methods to optimize screening on a cost per case ascertainment basis will be examined. There is evidence that there is an increasing incidence of endometrial cancer in the United States. Screening for endometrial lesions in the population is not done routinely, although methods are available for ascertaining endometrial pathology. The identification of groups with differential risk of incidence of endometrial lesions together with estimates to quantify this increase risk will be presented and the costs involved for screening on a selective basis studied. A study of measures of association used as indices of the relationship between the incidence of a given lesion and other traits will be done. The index of relative risk is used in the characterizing of subset in the population for which selective screening may be identified. An investigation of statistical methods for obtaining an estimate of this index in the presence of more than one risk factor will be carried out.